Science: Insect Front

Some little bug is going to find you some day. . . .

—Roy Atwell

The 1,000 professional exterminators who work in New York City last week generally felt that they were barely holding their own against the insect world. The verminous swarm which always threatens mankind has made great wartime gains due to shortages of insecticide and manpower and to heavy wartime travel (especially of insects aboard furloughed servicemen).

Manhattan harbors every known species of urban insect—and many of their country cousins. The battle against them costs $5,000,000 a year in labor alone, many millions more for weapons. Three-quarters of the city’s business buildings and apartment houses are constantly sprayed and fumigated.

The biggest human setback has been loss of pyrethrum, far & away the deadliest prewar insecticide, of which almost the entire supply came from Japan. The substitutes on which bug fighters now chiefly rely are the new Lethanes (not so deadly) and sodium fluoride (dangerous because poisonous to man). One of the most effective exterminators is ultra-deadly hydrocyanic gas, but against it there is a city ordinance.

Of the dozen bugs that give New Yorkers the most trouble, the termite and the brown dog tick are among the most menacing—their population is growing rapidly. But even in modern, skyscraping Manhattan, man’s worst insect enemies are still the ancient, hardy foes against which he has waged long and barely equal warfare—the cockroach, bedbug, ant, moth, silverfish.

Big Eaters. The 100,000,000-year-old cockroach, which outlived the dinosaur and many other prehuman contemporaries, has evolved into a superbug of almost incredible staying power. Its hard, slippery body is hard to grasp; its flat torso permits it to squeeze into the smallest cracks; its nimble legs give it unparalleled speed and shiftiness; its skin is so sensitive to light that even when blinded it infallibly finds a dark place to hide in. It can get along on so little oxygen that it lives for hours after its breathing tubes have been sealed; it is the only known creature that can live without vitamin A or C or nitrogen. Its voracity is the most catholic in the insect world—it eats paint, bedbugs, hair, grease, wallpaper, gold lettering on books, its own cast-off skin.

The surest weapon against the roach is extreme temperature. The insect thrives between 70 and 80° Fahrenheit, but can be killed by dry air at 86°, becomes numb at 35°, dies at 23°. It is also very susceptible, when it can be reached, to poison. In Manhattan the most common varieties of roach are the American (an inch and a half long) and the German (half as large) ; the German is locally known as the “Croton bug” because it first invaded the city in large numbers when holes were cut in walls for water pipes, at the time the Croton Dam was built for a civic water supply. In spite of its appetite, the cock roach’s chief danger to man is not destructiveness but food contamination.

The bedbug is harder to poison. Unlike the roach, it is an epicure: it feeds on human blood. A loathsome, wingless insect, it is light brown and flat before feeding, swells up and turns mahogany afterward. Chief difficulty in fighting bedbugs : housewives hate to admit their presence. Though the common bedbug hurts little except family pride, a relative known as the “kissing bug” transmits Chagas’ disease (a deadly parasitic disease originating in Brazil) to human beings. A Lethane spray is the most effective bedbug poison.

Country Visitors. By far the most damaging insect, and most at home in modern civilization, is the clothes moth. It has been known to eat house insulation as well as clothes, rugs, etc. (it is destructive in the larval stage only). Best weapons against the moth are sunlight, moth balls or flakes,paradichlorobenzene. Chemists have recently developed effective new methodsfor permanent mothproofing of wool — for postwar use.

The hardest insect to control is the ant. Manhattan is infested with small red ants; they often nest in buildings instead of in the ground, eat sweets, meat, greasy garbage. The most successful poison against them is thallium sulfate baited with sugar — but all prewar supplies of thallium sulfate came from Germany and France.

Technology has been a boon to the silverfish. This swift, slithery, scaly insect, less than half an inch long, is an old inhabitant of forests, where it nests under stones and in the bark of dead trees. But it has recently migrated to the city in prodigious numbers because of its fondness for a modern product: rayon. It also likes linen, starched cotton, flour. Unlike the moth, which feeds slowly, the silverfish is a ravenous eater, can make lacework of a shirtfront in a few hours. It is also very hard to starve out ; a well-stuffed silverfish can go as long as ten months without food. Recently an entomologist, having failed toget very far with poison, devised an ingenious silverfish trap: he put flour in a glass jar, taped the outside of the jar. The silverfish easily climb the adhesive tape to get at the flour, but the inside glass walls of the jar are too slippery for them to climb out.

Veteran exterminators are interested but not enthralled by the idea of such war-born insecticides as DDT (TIME, June 12). They are inclined to think bugs will survive DDT, too.